Metallized and non-metallized films are commonly used in a variety of electrical, packaging and decorative applications. Although the application field is quite broad, the desired properties of the different films are basically the same. These desired properties include mechanical strength, thermal and chemical resistance, abrasion resistance, moisture and oxygen barrier, and surface functionality that aids wetting, adhesion, slippage, etc. As a result, a multitude of hybrid films have been developed to service a wide range of applications.
In general, hybrid metallized and polymer coated films utilize a variety of production methods. For example metallized polymer films are usually corona-, flame-, or plasma-treated, to promote adhesion of the metal to the polymer surface (U.S. Pat. Nos. 5,019,210 and 4,740,385); or ion beam-treated and subsequently electron beam-charged to promote adhesion and flattening of the film onto a substrate by electrostatic force (U.S. Pat. No. 5,087,476). Polymer coatings that serve various functions such as printability, adhesion promotion, abrasion resistance, optical and electrical properties, have been produced using various techniques that include thermal cure, reactive polymerization, plasma polymerization (U.S. Pat. No. 5,322,737), and radiation-curing using ultra-violet and electron beam radiation (U.S. Pat. Nos. 5,374,483; 5,445,871; 4,557,980; 5,225,272; 5,068,145; 4,670,340; 4,720,421; 4,781,965; 4,812,351; 4,567,083; and 5,085,911). In such applications, a monomer material is applied using conventional techniques of roll coating, casting, spraying, etc., and the coating is subsequently polymerized under atmospheric pressure conditions.
More recently, a new technique has been developed that allows the formation of radiation-curable coatings in the vacuum using a flash evaporation technique that leads to the formation of a vapor-deposited thin liquid monomer which can be radiation-cured (U.S. Pat. Nos. 4,842,893; 4,954,371; and 5,032,461 and European Patent Application 0 339 844). This technique overcomes the limitations of conventional techniques for applying the liquid monomers and requires relatively low doses of radiation for polymerization.
The vacuum polymer coating technique as described in the above references was found to have some critical limitations on certain mechanical, thermal, chemical and morphological properties that can reduce their usefulness in packaging films, capacitors, metal evaporated magnetic tapes and optically variable films. The invention disclosed herein overcomes these problems and extends the one-step polymer and metal vacuum coating technique to new functional products with a unique set of properties.